Manufacture of long chain saturated aliphatic hydrocarbons



the decomposition temperature of the peroxide.

United States Patent 6 MANUFACTURE OF LONG CHAIN SATURATED ALIPHATIC HYDROCARBONS Bernard S. Wildi, Dayton, Ohio, assignor to Monsanto Chemical Company, 'St. Louis, Mo., a corporation of Delaware No Drawing. Application September 29, 1954, Serial No. 459,209

Claims. (Cl. 260--676) This invention relates to the'manufacture of hydrocarbons. In one embodiment the invention pertains to the thermal decomposition of lauroyl peroxide in diphenylmethane solvent to produce high yields of docosane.

Long chain aliphatic hydrocarbons are often needed for research work and for industrial use. However, it is almost impossible to obtain same from natural sources because those natural sources provide such hydrocarbons only in admixture with a large number of other hydrocarbons and separation of the mixture into pure components is extremely difiicult and often impossible. While various procedures are available for synthesizing pure long chain aliphatic hydrocarbons, there is still great need for a straight-forward procedure giving such hydrocarbons in reasonable yields and without contamination by materials difiicult to separate therefrom.

An object of this invention is to manufacture hydrocarbons. Another object of the invention is to make pure long chain aliphatic hydrocarbons. A further object is to synthesize long chain aliphatic hydrocarbons in high yield. Still another object is to provide a process for making long chain paraflin hydrocarbons from comparatively cheap and readily available raw materials. Other objects and advantages of the invention will be apparent to those skilled in the art from the accompanying disclosure and discussion.

In accordance with a preferred embodiment of the present invention, an aliphatic acyl peroxide having at least 3 carbon atoms per acyl group is dissolved in a diphenylmethane, and the resulting solution is heated to As a result of decomposition and decarboxylation of the peroxide and interaction with the diphenylmethane solvent an open chain hydrocarbon is formed having 2 carbon atoms less than the peroxide. For example, lauroyl peroxide in diphenylmethane gives docosane as the major product. Small quantities of hendecane and l,1,2,2,-tetraphenylethane, as well as carbon dioxide, are also formed. The long chain docosane is obtained in high yield, and is easy to separate from the reaction mixture.

This invention is generally applicable to peroxides of aliphatic carboxylic acids. Aliphatic diacyl peroxides, also termed herein aliphatic acyl peroxides, having at least 3 carbon atoms per acyl group and the hydrocarbon portions of the acyl groups being straight chain or branched chain, can be converted to hydrocarbons having the hydrocarbon substituents of the acyl groups joined together, i. e., the

o 0 -o o i group has been eliminated and the hydrocarbon residues joined to each other at the point of their former attachment to said group. The peroxides of the various saturated aliphatic carboxylic acids are Well-known, and can be easily made from readily available acids. Thus, by

converting ordinary acids, e. g., hexanoic acid, butyric acid, lauric (i. e., dodecanoic) acid to their peroxides,

and then subjecting said peroxides to thermal decomposition while dissolved in diphenylmethane or a substituted diphenylmethane, a simple process is provided for making aliphatic hydrocarbons having double the number of carbon atoms present in the acid minus two. The bydrocarbon groups of the acid, and thus of the peroxides, can be straight chain or branched chain. Thus, for example, the invention is applicable to n-butyroyl peroxide, isobutyroyl peroxide, sec.-butyroyl peroxide, and tert.-butyroyl peroxide. Similarly, the peroxides of higher acids having straight chains and branched chains having various configurations are treated in accordance with the invention to give corresponding long chain hydrocarbons. It is preferred to employ peroxides of acids containing at least 10 carbon atoms in the acid mole cule, and preferably not above 30 carbon atoms in the.

acid molecule. The peroxides, of course, have twice the number of carbon atoms. While the invention is especially applied to the unsubstituted aliphatic acyl peroxides, it can also be applied to aliphatic acyl peroxides having simple snbstituents on the hydrocarbon portions of the molecule that do not interfere with the reaction.

The temperature of reaction is dependent upon thetemperature at which the particular peroxide undergoes thermal decomposition. For example, lauroyl peroxide is readily subjected to the reaction at C. Most peroxides are reactive for the purposes of this invention at a temperature within the range of 30 to C. it is not necessary and in fact it is undesirable to employ a temperature appreciably above that at which the reaction will take place readily. Those skilled in the art will recognize of course that suitable precautions should be taken in view of the tendency of organic peroxides to undergo decomposition with explosive violence. In carrying out the invention a gradual heating of a solution of the peroxide in the diphenylmethane is effective to initiate and maintain the reaction at a controlled rate.

Diphenylmethane is the preferred solvent for the practice of the invention. However, also useful are substituted diphenylmethanes whose substituents do not interfere with the reaction; those containing chlorine, alkyl and nitro groups on one or both of the phenyl radicals are usually satisfactory. Alkyl groups of from 1 to 6 carbon atoms and higher are satisfactory, including normal and branched chain alkyl groups.

Usually the quantity of a diphenylmethane necessary to dissolve an aliphatic acyl peroxide is sufiicient for effecting the reaction. Often the weight of diphenylmethane will exceed the weight of peroxide.

Along with the principal long chain hydrocarbon product, lesser amounts, usually quite small, of the corresponding short chain hydrocarbon having half the number of carbon atoms are formed. These short chain hydrocarbons have the configuration of the alkyl substituent of the peroxide and contain 1 less carbon atom than the aliphatic carboxylic acid from which the peroxide is derived. The diphenylmethane also tends to undergo some reaction to form a l,l,2,2-tetraarylethane condensation product. Thus, in the case of diphenylmethane itself, some l,1,2,2-tetraphenylethane is obtained. By Way of example, from the interaction of lauroyl peroxide with diphenylmethane, docosane (C22H4a) is obtained as the principal product together with small amounts of hendecane (C11H24) and 1,l,2,2-tetradiphenylethane.

The following example is offered to illustrate one preferred embodiment of the invention. It will be appreciated that changes can be made in the proportions, peroxide, and the diphenylmethane compound without l 'atented' July 31, 1956 departing from the invention in its broadest aspects. The Parts are by weight.

Example Thirty parts lauroyl peroxide, i. e.,

(CH3 (CH2) 1oCO)202 was dissolved in 400 parts diphen-ylmethane, i. e., (CGH5)2CH2. The solution was gradually heated to a temperature of 75 C. and maintained at that temperature for a period of 8 hours. The resultant reaction mixture contained the following reaction products. Yields are per cent of moles theorectically obtainable if all the lauroyl peroxide were converted to the specified reaction product.

Yield, Percent of Theory Product Parts Docosane 77 Hendecane l2 1,1,2,2-Tetraphenylethane 2. A process for forming long chain saturated aliphatic hydrocarbons which .comprises subjecting to thermal decomposition a solution of a saturated aliphatic acyl peroxide having at least 3 carbon atoms per acyl group in diphenylmethane.

3. A process which comprises subjecting the peroxide of a saturated aliphatic carboxylic acid, said acid containing at least 3 carbon atoms, to thermal decomposition while dissolved in a diphenylmethane, and recovering as product of the process a parafiinic hydrocarbon containing 2. 1 minus 2 carbon atoms where n is the number of carbon atoms in said acid.

4. A process which comprises dissolving lauroyl peroxide in diphenylmethane, heating the resulting solution to a temperature'in the neighborhood of 75 C. for a time sufficient to eflect decomposition of said lauroyl peroxide, and recovering as the major reaction product docosane in high yield.

5. A process according to claim 1 wherein said peroxide is the peroxide of a saturated aliphatic carboxylic acid containing at least 10 carbon atoms per molecule of acid.

References Cited in the file of this patent Kharasch et al.: J. Org. Chem. vol 10, pages 386 393 (1945). (Abstracted in Chem. Abstracts, vol. 40 (1946), page 1783.) a

Taylor et al.: J. Chem. Phys, vol. 8, pages 543-546 (1940). (Abstracted in Chem. Abstracts, vol. 34 (1940), page 57313.) 

1. A PROCESS FOR FORMING LONG CHAIN SATURATED ALIPHATIC HYDROCARBONS WHICH COMPRISES SUBJECTING TO THERMAL DECOMPOSITION A SOLUTION OF A SATURATED ALIPHATIC ACYL PEROXIDE HAVING AT LEAST 3 CARBON ATOMS PER ACYL GROUP IN A DIPHENYLMETHANE. 